This invention relates to loudspeakers, and, more particularly, to a loudspeaker having the combination of an o-ring and C-clamp for removably mounting the outer end of the surround of the loudspeaker to the frame.
Loudspeakers generally comprise a frame, a motor structure, a diaphragm, a lower suspension or spider and a surround. In one common type of speaker, the motor structure includes a permanent magnet mounted between a top plate and a back plate, a pole piece centrally mounted on the back plate and a voice coil axially movable with respect to the pole piece. The voice coil includes a hollow, cylindrical-shaped former having an outer surface which receives a winding of wire.
One end of the diaphragm is connected to the surround or upper suspension, which, in turn, is mounted to the upper end of the frame. The lower suspension or spider is connected at one end to a seat formed in the frame at a point between its upper and lower ends. The free ends of the diaphragm and spider are mounted to the voice coil and support it within an air gap between the pole piece and top plate of the motor structure, with the former of the voice coil concentrically disposed about the pole piece. In some speaker designs, a dust cap is mounted to the diaphragm in position to overlie the voice coil and pole piece to protect them from contaminants.
In the course of operation of a speaker of the type described above, electrical energy is supplied to the voice coil causing it to axially move relative to the pole piece and within the air gap formed between the top plate and pole piece. The spider and surround move with the excursion of the voice coil and function to maintain the voice coil centered to avoid rocking or rubbing against the pole piece of the motor.
Surrounds are typically constructed from materials such as rubber, compressed foam rubber, corrugated cloth, paper, plastic and other materials. In many speaker designs, surrounds are also referred to as a xe2x80x9crollxe2x80x9d and comprise a semi-circular corrugation formed of rubber. These types of surrounds or rolls have a radially outwardly extending outer edge which is conventionally glued to a flat extension or rim formed at the upper end of the frame of the loudspeaker which also acts as the mounting flange for the speaker. This construction sacrifices a significant amount of diaphragm area, compared to the overall, outside diameter of the speaker, and a reduction in diaphragm area adversely affects the output and efficiency of the speaker.
Another issue with the construction of loudspeakers having the surround glued to the frame involves difficulties in repairing or replacing one or more of the moving parts. Conventionally, the surround, spider and diaphragm are cut away, and the frame and motor are stripped down with chemicals or hand scraped to remove adhesive residue. The new diaphragm, voice coil, surround and spider are then glued together and secured to the loudspeaker frame. This operation requires precise alignment and is usually performed by skilled technicians employing specialized gauges or alignment spacers. Additionally, care must be taken to replace the worn, damaged or outdated moving parts with ones which match the existing motor structure and frame, and can perform the intended task of the speaker, e.g. concert sound reinforcement, automotive sub-bass, home theater and the like.
U.S. Pat. Nos. 5,687,247 and 5,949,898 to Proni address many of the deficiencies of surround construction noted above. In these designs, the surround is removably attached to the outer edge of the upper end of the frame thus allowing a larger diameter surround to be used compared to the prior art. In turn, the effective area and linear displacement of the diaphragm is increased allowing for the design of long-excursion loudspeakers with enhanced performance characteristics. The method of attachment of the surround in the two Proni patents noted above includes, in some embodiments, the use of a flexible o-ring which engages an outer portion of the surround and forces it into contact with a recess formed in the outer edge of the frame. One advantage of this construction is that no adhesive is required, and the surround can be readily removed to permit access to the other elements of the speaker for repair or replacement.
Notwithstanding the improvements obtained with the design disclosed in the Proni patents noted above, some limitations remain. It has been found that the recess formed in the outer edge of the frame to receive the surround may have rough edges which can cause the surround to tear when it is forced into place by the o-ring or during operation of the speaker. Additionally, the o-ring is susceptible to being dislodged from its position against the surround and within the recess in the frame. It is a flexible, resilient circular-shaped member, not unlike a rubber band, and is completely exposed on the exterior of the speaker. Particularly during installation of loudspeakers which incorporate the surround mounting structure of the Proni patents, such as subwoofers in automotive sound systems, the exposed o-ring may be dislodged from its position on the frame. In addition to physical contact with the o-ring, it can also be moved or dislodged during operation of the speaker especially in applications where the o-ring is used in high excursion speakers mounted within a box or enclosure. Substantial pressures are generated within the box interior in the course of speaker operation, and the o-ring must create an effective seal between the surround and frame for the speaker to function properly. These high pressures could result in sufficient movement of the o-ring to compromise the seal at the surround and frame and/or allow the surround itself to move, both of which would have significant negative effects on the performance and sound quality of the speaker.
It is therefore among the objectives of this invention to provide a loudspeaker having a secure but removable attachment between the surround and frame, which is easy to install and remove for repair or replacement of the moving parts of the speaker.
These objectives are accomplished in a loudspeaker including a frame formed with an upper end having a seat which receives the outer edge of a surround. The surround is retained within the seat by the combination of an o-ring in contact with the surround, and a C-shaped clamp having an upper arm which engages the o-ring and a lower arm releasably mounted to the upper end of the frame.
In one presently preferred embodiment, the outer edge of the surround is formed with a foot portion connected to an end segment, both of which rest against surfaces of the seat in the upper end of the frame. The o-ring engages the surround at the juncture of the foot portion and upper segment, forcing it against the frame seat. With the o-ring in place, the C-clamp is then installed such that its upper arm overlies the o-ring and the lower arm bears against a horizontally extending ledge forming part of the seat. Much of the clamping force exerted against the outer edge of the surround is provided by the o-ring, but the clamp also forces the o-ring against the foot portion of the surround. Additionally, the clamp completely covers the o-ring which protects it from being dislodged by contact during installation or transport of the loudspeaker, or during high excursion operation.
In an alternative embodiment, the continuous, annular C-clamp is replaced with a number of individual clamp segments each having the same cross section as the C-clamp but extending only part way along the circumference of the o-ring. A number of clamp segments are employed to retain the o-ring in place, and at least partially cover it, which are spaced from one another as desired.
Whether a continuous C-clamp or clamp segments are employed, a still further embodiment of this invention involves the addition of a channel structure at the upper or top end of the clamp(s). This channel structure is formed by an inner, annular lip and an outer ring which are spaced from one another to form a channel sized to receive a grill via an interference fit. The grill is a generally semi-circular shaped section of wire mesh which functions to cover and protect the surround and diaphragm from impact during use of the speaker.